Method of Installing an Expandable Tubular in a Wellbore

ABSTRACT

A method of installing an expandable tubular element in a wellbore comprises lowering the tubular element into the wellbore such that an annular space is formed between the tubular element and the wellbore wall, locating a first compound in the annular space, the first compound being adapted to cooperate with a second compound upon contact therewith so as to form an annular body anchoring the tubular element in the wellbore, radially expanding a section of the tubular element, and inducing the second compound to enter a portion of the annular space surrounding said expanded tubular section. An unexpanded section of the tubular element is disconnected from the expanded tubular section and removed from the expanded tubular section.

The present invention relates to a method of installing a tubular element in a wellbore whereby the tubular element is radially expanded in the wellbore so as to form an expanded tubular section and an unexpanded tubular section, and whereby an annular space is formed between the tubular element and the wellbore wall.

In the description hereinafter, the term “casing” is used to refer either to a wellbore casing or to a wellbore liner. Wellbores for the production of hydrocarbon fluid generally are provided with one or more casings to stabilise the wellbore wall and/or to provide zonal isolation. Cement is pumped into the wellbore to seal the annular space and to fix the casing in the wellbore. Generally, several casings are set at different depth intervals, in a nested arrangement whereby the diameter of each subsequent casing is smaller than the diameter of the previous casing in order to allow lowering of the subsequent casing through the previous casing.

Recently it has become practice to radially expand tubular elements in the wellbore. For example, a casing is expanded to allow a larger available working space in the wellbore, or a tubular element is expanded against an existing casing to form a tubular clad and to serve as a production conduit for hydrocarbon fluid. Also, it has been proposed to construct a monodiameter well by radially expanding each casing to substantially the same diameter as the previous casing. It is thus achieved that the available inner diameter of the casings is substantially constant throughout the wellbore depth, as opposed to the conventional nested arrangement whereby the available diameter decreases stepwise with each subsequent casing. The monodiameter concept is particularly of interest for very deep wellbores or for extended reach wellbores. To expand the tubular element in the wellbore, an expander of larger diameter than the inner diameter of the unexpanded tubular element is pumped, pushed or pulled through the tubular element, sometimes with combined rotation of the expander.

In applications whereby a casing is expanded in the wellbore, there is generally a need to pump cement, or another suitable hardening fluid, into the annular space between the casing and the wellbore wall in order to seal and fix the casing in the wellbore. The cement can be pumped into the annular space before or after radial expansion of the casing, but in most applications it will be preferred to pump the cement before expansion of the casing since adequate pumping of cement into the narrow annular space after the expansion process may not be feasible. Such procedure, however, limits the time period available for the expansion process since expansion of the casing is no longer feasible after the cement has hardened. In view thereof it is practical to use cement with a low hardening rate. However, if the expansion process is delayed after the cement has been pumped into the annular space, for example due to unforeseen circumstances, there is still a risk that the cement hardens before the expansion process is finalised. Hardening of the cement before the entire tubular element has been expanded can lead to the situation that the unexpanded section of the tubular element forms an obstacle in the wellbore. Thus, although in most applications it will be desirable to expand the whole tubular element, there is still a need for a suitable expansion method if only a section of the tubular is expanded, either planned or unplanned.

It is therefore an object of the invention to provide an improved method of installing an expandable tubular element in a wellbore, which method overcomes the aforementioned drawback.

In accordance with the invention there is provided a method of installing an expandable tubular element in a wellbore, the method comprising:

-   -   lowering the tubular element into the wellbore whereby an         annular space is formed between the tubular element and the         wellbore wall;     -   locating a first compound in the annular space, the first         compound being adapted to cooperate with a second compound upon         contact therewith so as to form an annular body anchoring the         tubular element in the wellbore;     -   radially expanding a section of the tubular element;     -   inducing the second compound to enter a portion of the annular         space surrounding said expanded tubular section; and     -   disconnecting an unexpanded section of the tubular element from         said expanded tubular section, and removing the unexpanded         tubular section from the expanded tubular section.

In this manner its is achieved that the annular body is only formed in the portion of the annular space surrounding the expanded tubular section, so that only the expanded tubular section becomes anchored in the wellbore. The unexpanded section of the tubular element has not become anchored in the wellbore, and therefore still can be removed from the wellbore or can be lowered through the expanded section deeper into the wellbore. Suitably the annular body also functions to seal the expanded tubular section in the wellbore.

The tubular element preferably is provided with container means containing said second compound, wherein the container means is induced to release the second compound into said portion of the annular space upon radial expansion of said section of the tubular element. The second compound can be released from the container means, for example, by deformation of the container means upon radial expansion of said section of the tubular element.

The container means preferably includes at least one annular container surrounding the tubular element. More preferably the container means includes a plurality of annular containers axially spaced along the tubular element, each container extending around the tubular element.

If the tubular element has an inlet section for inflow of hydrocarbon fluid into the tubular element, it is preferred that the container means is absent from said inlet section. In order to allow unobstructed flow of hydrocarbon fluid to the inlet section, suitably the first compound is removed from a portion of the annular space surrounding said inlet section.

In a preferred embodiment the second compound is an activating compound and the first compound is a fluidic compound adapted to harden upon contact with the activating compound.

Also, the fluidic compound can be adapted to slowly harden by itself, whereby the activating compound functions to accelerate the hardening process. In this manner it is achieved that the activating compound needs to be injected into the annular space at discrete locations only, instead of continuously along the length of the expanded tubular section. The fluidic compound is subjected to accelerated hardening at the discrete locations, thereby providing sufficient initial anchoring functionality for the tubular element. Full anchoring functionality is provided after hardening of the remainder of the fluidic compound by itself.

Apart from anchoring the tubular element in the wellbore, suitably the annular body of hardened compound also provides zonal isolation in the wellbore, i.e. the annular body prevents fluid communication between different earth layer traversed by the wellbore.

In a preferred embodiment the fluidic compound and the activating compound are adapted to chemically react with each other so as to form said annular body. Alternatively the activating compound is a catalyst adapted to trigger or to accelerate hardening of the fluidic compound.

It is to be understood that the term “fluidic compound” refers to a compound which can be pumped into the wellbore in a stream, for example a stream of liquid, a stream of solid particles, or a stream of solid particles in a carrier fluid.

Suitable systems of fluidic compound and corresponding activating compound for use in the method of the invention, are the two-component systems outlined hereinafter.

A) Two-Component Cement Systems.

Suitable examples of two-component cement systems are Liquid Stone (trade mark) and S-Mix (trade mark).

Liquid Stone is described in WO 95/199 42; U.S. Pat. No. 5,447,197; U.S. Pat. No. 5,547,506; U.S. Pat. No. 6,173,778 and U.S. Pat. No. 6,145,591. These systems include a cement slurry kept in liquid state by suitable retardation for a long time and then activated by addition of an activating compound to set and harden when necessary. The cement slurry can be Portland oil well cement (ISO Classes A-H), ground granulated blast furnace slag (GGBFS), or slagment which is a mixture of Portland cement and GGBFS. Sodium Silicate can be used as the activating compound in these systems.

S-Mix is described in WO 94/09249; WO 94/09250; WO 94/09251; U.S. Pat. No. 5,361,842; U.S. Pat. No. 5,361,842; U.S. Pat. No. 5,476,144; U.S. Pat. No. 5,409,063; U.S. Pat. No. 5,409,064; U.S. Pat. No. 5,411,092 and U.S. Pat. No. 5,423,379. The fluidic compound is a dormant cement slurry including GGBFS, either with or without Portland cement. The activating compound can be an alkaline solution, such as Caustic Soda, Soda ash or Sodium Silicate solutions.

B) Two-Component Resin Systems.

These systems include thermosetting resins such as epoxies, polyurethanes, and polyesters, whereby a suitable catalyst is used as activating compound. A comprehensive review of thermosetting resins is given in ‘Engineered Materials Handbook, Desk Edition, ASM International, 2nd edition 1998, ISBN 0-87170-283-5, Chapter 3, page 250-282, “Thermoset engineering plastics and elastomers”, and Chapter 7, Page 631-672, “Sealants”.

C) Two-Component Gel Systems.

Suitable examples of such systems are Chromium cross linked polyacrylamides such as Maraseal (trade mark) or Marcit (trade mark); polyvinyl alcohol (PVA) cross-linked with a special (photosynthesized) agent, such as disclosed in US 2002/0128374 and referred to as Wondergel (trade mark); oil based thermal insulating gels, such as disclosed in U.S. Pat. No. 4,258,791; and in-situ gelleable compositions, normally used for shut-off of steam injectors, for example as disclosed in U.S. Pat. No. 4,858,134.

The invention will be described hereinafter in more detail by way of example, with reference to the accompanying drawings in which:

FIG. 1 schematically shows a wellbore in which an expandable casing is installed according to an embodiment of the method of the invention;

FIG. 2 schematically shows detail A of FIG. 1 indicating an annular container provided at the outer surface of the casing;

FIG. 3 schematically shows the wellbore of FIG. 1 after radial expansion of a section of the casing; and

FIG. 4 schematically shows the casing of FIG. 1 during removal of an unexpanded section thereof from the wellbore.

In the Figures like reference numerals relate to like components. Furthermore, it is to be understood that the terms “below”, “above”, “upward” and “downward” refer to wellbore depths measured along the longitudinal axis of the wellbore and relative to surface.

Referring to FIGS. 1-4 there is shown a wellbore 1 formed in an earth formation 2, and an expandable steel casing 4 extending from surface into the wellbore 1 thereby defining an annular space 3 between the casing 4 and the wall of the wellbore 1. The annular space 3 contains a body of a fluidic compound in the form of Portland cement adapted to react with an activating compound in the form of Sodium Silicate so as to form a hardened cement substance. The casing 4 is provided with a plurality of annular containers 6 regularly spaced along the casing 4. Each container 6 extends around the casing 4 and includes a steel inner wall 8 and a steel outer wall 10 (FIG. 2), the walls 8, 10 being welded together at their respective end portions 12. The outer wall 10 is provided with a plurality of grooves (not shown) forming sections of reduced strength intended to rupture upon deformation of the container due to radial expansion of the casing 4. Each container 6 contains a volume 14 of said activating compound.

The casing 4 has a lower portion 15 in which an expander 16 for radially expanding the casing 4 is located. The expander 16 has a frusto-conical outer surface, with diameter varying from D1 at the upper end of the expander to D2 at the lower end of the expander, whereby D1 corresponds to the inner diameter of the unexpanded casing and D2 corresponds to the inner diameter of the expanded casing. The lower casing portion 15 has been pre-expanded using a suitable tool (not shown) to allow insertion of the expander 16 therein. Further, the lower casing portion 15 is provided with a packer 17 sealing the lower end of the casing 4.

A cutter tool 18 is connected to the lower end of the expander 16, the cutter tool 18 having a plurality of cutters 20 operable between a radially retracted mode whereby the cutters 20 are free from the inner surface of the casing 4, and a radially expanded mode whereby the cutters 20 are biased against the inner surface of the casing 4. The cutter tool 18 is rotatable about the longitudinal axis of the casing 4 so as to enable cutting of the casing when the cutter tool 18 is driven in rotation by a conduit 22 (referred to hereinafter) whereby the cutters 20 are in the expanded mode.

The expander 16 is connected to a fluid pump (not shown) at surface via a conduit 22 extending through the casing 4. Further, the expander 16 has a through-bore 24 aligned with the interior of the conduit 22 to provide fluid communication between the portion of the interior space of the casing 4 between the expander 16 and the packer 17, and the fluid pump at surface.

During normal operation the fluid pump at surface is operated to pump a selected fluid, for example brine, into the lower casing portion 15 so as to increase the fluid pressure in the lower casing portion 15. Upon the fluid pressure reaching a threshold value, the expander 16 starts moving upwardly through the casing 4 due to the increased fluid pressure, thereby gradually expanding the casing 4. Thus, at each stage during the expansion process the casing 4 has an expanded lower section 26, an unexpanded upper section 28, and an expansion front 29 opposite the expander 16. The expansion front 29 forms a transition between the expanded and unexpanded sections 26, 28.

Each container 6 bursts open upon arrival of the expansion front 29 at the level of the container 6 due to rupturing of the outer wall 10 of the container 6. As a result the activating compound is expelled from the container 6 and becomes mixed with the fluidic compound in the annular space 3. The activating compound thereby reacts with the fluidic compound and forms a body 30 of said hardened substance in the annular space 3.

If the expansion process has to be stopped, for example in the event that the expander 16 has become stuck in the casing 4, the cutter tool 18 is operated whereby the cutters 20 are moved to their expanded mode and the cutter tool 18 is rotated via conduit 22 from surface in order to cut the casing 4 and thereby to separate the expanded lower casing section 26 from the unexpanded upper casing section 28. The conduit 22 may have to slackened-off before rotation is started.

The body 30 of hardened substance in the annular space 3 surrounding the expanded lower casing section 26 forms an adequate seal and prevents flow of formation fluid between the expanded casing portion 26 and the wellbore wall. Further, the body 30 of hardened substance anchors the expanded casing section 26 in the wellbore 1.

Referring to FIG. 4, in a next step the unexpanded upper casing section 28, which is now separate from the expanded lower casing section 26, is removed from the wellbore 1. Removal is possible since the containers 6 surrounding the unexpanded casing section 28 are intact, therefore the fluidic compound in the portion of the annular space 3 surrounding the unexpanded casing section 28 has not transformed into a hardened substance as it has not mixed with the activating compound.

Instead of the cutter tool being arranged below the expander (as shown in the Figures), the cutter tool can be arranged above the expander, i.e. at the up-hole side of the expander.

In an alternative embodiment of the method of the invention, the first compound includes a swelleable elastomer, and the second compound includes a selected fluid capable of inducing swelling of the elastomer. The elastomer can be, for example, EPDM rubber and the selected fluid can be a hydrocarbon fluid such as toluene. The elastomer can be provided to the outer surface of the tubular element in the form of a sleeve, or can be provided in the annular space in the form of a pack of swelleable elastomer particles. Suitable examples of elastomer/fluid combinations are disclosed in International patent application WO 03/008756.

In a further modification the selected fluid is a formation fluid, such as oil or water from the earth formation, and a protective coating encapsulates the elastomer particles (or the elastomer sleeve) to prevent direct contact of the elastomer material with the formation fluid. The container means described above contains a dissolving fluid adapted to dissolve the protective coating so that, after release of the dissolving fluid into the annular space, the coating is dissolved and the elastomer material swells due to contact with the formation fluid. 

1. A method of installing an expandable tubular element in a wellbore, the method comprising: a) lowering the tubular element into the wellbore whereby an annular space is formed between the tubular element and the wellbore wall; b) locating a first compound in the annular space, the first compound being adapted to cooperate with a second compound upon contact therewith so as to form an annular body anchoring the tubular element in the wellbore; c) radially expanding a section of the tubular element; d) inducing the second compound to enter a portion of the annular space surrounding said expanded tubular section; and e) after inducing the second compound to enter said portion of the annular space, disconnecting an unexpanded section of the tubular element from said expanded tubular section, and removing the unexpanded tubular section from the expanded tubular section.
 2. The method of claim 1, wherein the tubular element is provided with container means containing said second compound, and wherein the container means is induced to release the second compound into said portion of the annular space upon radial expansion of said section of the tubular element.
 3. The method of claim 2, wherein the container means is induced to release the second compound into said portion of the annular space upon deformation of the container means due to radial expansion of said section of the tubular element.
 4. The method of claim 2, wherein the container means includes at least one annular container surrounding the tubular element.
 5. The method of claim 4, wherein the container means includes a plurality of annular containers surrounding the tubular element, said annular containers being axially spaced along the tubular element.
 6. The method of claim 2, wherein the tubular element includes an inlet section for inflow of hydrocarbon fluid into the tubular element, and wherein the container means is absent from said inlet section.
 7. The method of claim 6, wherein the method further comprises removing said first compound from a portion of the annular space surrounding said inlet section.
 8. The method of claim 1, wherein the second compound is an activating compound and the first compound is a fluidic compound adapted to harden upon contact with the activating compound.
 9. The method of claim 8, wherein the fluidic compound is adapted to harden upon contact with the activating compound in a first period of time, and wherein the fluidic compound is adapted to harden in the absence of the activating compound in a second period of time longer than the first period of time.
 10. The method of claim 8, wherein the fluidic compound and the activating compound are adapted to chemically react with each other so as to form said annular body.
 11. The method of claim 1, wherein the step of disconnecting the unexpanded section of the tubular element from the expanded section of the tubular element comprises cutting the tubular element.
 12. The method of claim 1, wherein the step of removing said unexpanded section from said expanded section comprises retrieving the unexpanded section from the wellbore.
 13. (canceled) 